US weighs expanded tactical nuclear role to deter China, Russia — implications for Seoul, Tokyo

The US Defense Department is reviewing a new nuclear strategy that would expand the role of tactical nuclear weapons in defending allies against regional conflicts involving China or Russia, sources said. If adopted, the shift could alter how Washington operates its extended deterrence — commonly known as the nuclear umbrella — with significant implications for South Korea and Japan.

NBC News reported Wednesday, citing multiple anonymous sources, that a draft nuclear strategy overseen by Elbridge Colby, undersecretary of defense for policy, would increase the emphasis on short-range tactical nuclear weapons over long-range strategic ones.

The strategy is designed around scenarios in which a US ally comes under attack during a regional conflict with China or Russia. Rather than relying solely on the threat of intercontinental ballistic missiles and other strategic nuclear forces, the approach seeks to strengthen deterrence by expanding tactical nuclear options considered more likely to be used in practice.

A senior Defense Department official told NBC that "our judgment is that we need credible nuclear options," adding that President Donald Trump could strengthen deterrence by securing more practical and varied choices.

Should the strategy be adopted, South Korea and Japan — both of which rely on the US nuclear umbrella — could see notable changes to their security environment. A greater emphasis on usable tactical nuclear weapons could enhance the credibility of extended deterrence, but it could also heighten concerns about the possibility of nuclear use in Northeast Asia.

Colby was expected to visit US Strategic Command in Nebraska on Wednesday to discuss the strategy in a closed-door meeting, sources said. Strategic Command oversees US nuclear forces and deterrence strategy.

Tactical nuclear weapons are small nuclear devices designed to strike limited targets — such as enemy troops or military facilities — on the battlefield. Strategic nuclear weapons, by contrast, carry massive destructive power capable of targeting entire cities or nations and ending a war outright.

Colby has long argued that US nuclear doctrine relies too heavily on long-range strategic threats, undermining real deterrence. He has maintained that smaller tactical warheads capable of striking specific battlefield targets offer a more realistic option for defending allies than strategic weapons aimed at capital cities or major population centers.

A senior Defense Department official echoed that view. "For extended deterrence to be credible, it must provide nuclear capabilities that political leaders would actually consider using," the official said. "Otherwise, the only options left for leadership are extreme responses that adversaries won't believe — and deterrence breaks down."

However, the proposed expansion of tactical nuclear weapons has drawn considerable criticism. Analysts have long warned that tactical weapons carry a lower threshold for use than strategic ones, raising the risk that a conventional conflict could escalate into a nuclear exchange.

Concerns have also emerged within the United States. Some argue the approach could in fact limit a president's options in situations that call for long-range strategic forces, potentially weakening overall readiness.

A senior congressional official told NBC the strategy runs counter to Trump's stated goal of making nuclear deterrence great again. "This is a weak approach that narrows options at a time when we need more choices and more capability," the official said.